As if Zeus wasn't already a torment, the insidious banking trojan may become even more prolific now that its source code has been leaked on at least two underground forums, according to researchers at Denmark-based CSIS. Peter Kruse, writing on the company's blog, said the source code for the Zeus toolkit is "freely available for inspection, inspiration or perhaps to be compiled and used in future attacks." He expects the leakage to cause the trojan to become more pervasive. One likely can expect the price to fall too. McAfee researchers in September said the Zeus builder toolkit was going for between $700 and $1,500.